Variable resistance device



July 6, 1954 R, E, BROWN 2,683,202

VARIABLE RESISTANCE DEVICE Filed April 2, 1953 2 Sheets-Sheet 1 RALPH E. BROWM 93 INVENTOR.

July 6, 1954 R. E. BROWN 2,683,202

VARIABLE RESISTANCE DEVICE Filed April 2 1953 2 Sheets-Sheet 2 Magri?.

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RALPH 5. BRMW,

INVENTOR.

Patented July 6, 1954 UNITED STATES rrsNr oFFIcE VARIABLE RESISTANCE DEVICE Ralph E. Brown,

Los Angeles, Calif., assignor to Genisco, Inc., Los Angeles, Calif., a corporation Application April 2, i953, Serial No. 346,351

3l Claims. 1

This invention relates to potentiometers, voltage dividers, rheostats and similar variable resistance devices for various uses including use in instruments, measuring devices, and control systems.

The utility of the invention resides not only in vits basic purpose of providing variable resistance in an electric circuit, but also, and more important, in the fa t that it eliminates certain disadvantages that are inherent in prevailing types of variable resistance devices that incorporate a wiper movable along a resistor. Coniiicting considerations arise in the construction of such a device because, on the one hand, the movable wiper must exert appreciable pressure against the co-acting resistor to maintain clef'- trical communication between the wiper and resistor, and, on the other hand, the greater the wiper pressure provided to insure continuous electrical communication, the greater the wear of both the wiper and the resistor and the greater the actuating force required to move the wiper. Another coniict is found in the fact that a relatively small area of mutual contact between the wiper and resistor is usually desirable to minimize wear, but the smaller the area of mutual Contact, the greater the possibility that the wiper will be isolated by a minute dead spot on the resistor or by an intervening particle of non-conducting foreign material.

The present invention resolves both these confiicts, completely eliminates the usual rubbing friction created by a wiper, avoids the usual causes of wear along the resistor, minimizes theA required actuating force, and practically elimi-I nates any possibility of circuit interruption arising from failure of the wiper to maintain contact with the resistor.

Basically, all of these advantages are accomplished by providing a rst rotary member with a flexible conductor connected thereto forY wrapping contact with its periphery, a second movable member toi-eed or take up the conductor according to the direction of rotation of the first member, these three elements being in combination with a resistor positioned on one of the twomembers to be progressively snorted or viceversa when the two members move to shift the iiexible conductor. To use this combination as a simple rheostat, it is merely necessary to connect the conductor and the resistor into the cir- Cuit that is to be controlled. An importantfeature of the invention is that the resistor may be on the rotary member, as distinguished from the second take up member, and may be woundspirally thereon.; Thus the resistor mayV be wound around the rotary member with any number of spiral turns to provide resistance progressively variablev over any number of revolutions of the rotary. member. By virtue of such an arrangement,the range of resistance variation is not limited to 360 degrees of rotation of the rotary member.

When the invention is embodied in a voltagedividing potentiometer, the combination includes two resistors, one being on the periphery of the first rotary member and the other being mounted on the second member. Preferably the second member is also a rotary member. Thus each of the two rotary members alternately serves as means to feed out the flexible conductor, or to take up the iiexible conductor according to its direction or" rotation. The two rotary members rotate simultaneously and may be arranged either to rotate in the same direction, or to rotate simultaneously in opposite directions. Here again a feature of the invention is that the two rotary members may be oi cylindrical configuraa'tion with the corresponding resistor wound thereon to form a plurality of spiral turns so that the change in resistance may extend progressively over more than 360 degrees of rotation of the two rotary members.

A further advantage of the invention is that it .is especially suitable for embodiment in an accelerometer as will be explained. The various features and advantages of the invention will be apparent in the following detailed description considered with the accompanying drawing In the drawings, merely illustrative:

Figure 1 is a sectional view taken along the line I-I of Figure 2, illustrating one embodiment of the invention as a voltage dividing potentiometer;

Figure 2 is a diametrical section taken as indicated by the line 2-2 of Figure l;

Figure 3 is a fragmentary view similar to Figure l showing how the construction may be modified to provide a simple variable resistor as distinguished from a voltage divider;

Figure 4 is a simplified perspective view of the essential mechanism of the invention embodied as a voltage dividing device having a range of progressive resistance variation extending over several rotations;

Figure 5 is a fragmentary longitudinal sectional view showing the construction at one end of one of the rotary members shown in Figure fi;

Figure S is a similar fragmentary sectional view showing the construction at the other end of the rotary member;

Figure 7 is a view similar to Figure e, showing a rotary variable resistance device as distinguished from a voltage divider, the variable resistance device providing a progressive resistance change extending over several rotations of the device;

Figure 8 is a perspective view of the essential parts of the invention as embodied in an accelerometer;

which are to be regarded as Figure 9 is a plan view of the accelerometer mechanism shown in Figure 8;

Figure 10 is a sectional view of the complete accelerometer including the accelerometer houslng;

Figure 11 is a wiringdiagram of the basic Voltage dividing arrangement found in some of the foregoing illustrated embodiments of the invention; and

Figure 12 is wiring diag-ram of a variable resistance arrangement found in the other embodiments.

The embodiment of the invention illustrated in Figures 1 and 2 comprises a potentiometer of the voltage-dividing type. The potentiometer is housed in a suitable casing comprising a shallow cylindrical shell and a circular cover plate 2l attached thereto by suitable screws 22. This casing may be made of any suitable material, but preferably will be made of a non-conducting plastic.

Suitably mounted inside the described casing is a pair of movable members interconnected by a llexible conductor in such manner that simultaneous movement of the two members causes the conductor to peel off of one and to wrap onto the other with consequent variable shorting of resistor means mounted on the periphery of at least one of the two members. In this instance, it is contemplated that both of the members will be rotary and a feature of the specific construction shown in the drawings is the use of seg.- mental rotary members by virtue of which the device may be relatively compact.

As best shown in Figure 1 the two rotary members comprise a segmental member, generally designated 25, mounted on a pivot pin 26 and a second similar segmental member, generally designated 21, mounted on a second pivot pin 2t. Preferably each of the segmental members and 21 is of open construction comprising a pair of arm portions 35 extending from a hub portion 3l and an arcuate portion 32 interconnecting the outer ends of the two arm portions.

It is contemplated that the two rotary members 25 and 21 will be operatively interconnected for simultaneous rotation in opposite directions and various mechanical interconnections may be employed for this purpose in various practices of the invention, With the two rotary members operatively interconnected, they may be rotated in unison by actuating force applied to only one of the members. Such actuating force may be applied manually or may be applied automatically, for example, when the potentiometer is a component of an automatic control system. For the purpose of illustration, the potentiometer shown in Figures 1 and 2 is controlled manually by a knob 35 which may be formed with a radial point 36 for reference to a suitable arcuate scale (not shown) on the exterior of the cover 2 i.

The manually operable knob 35 is mounted on the outer end of the pivot pin 26, the pivot pin being journaled in a bore 31 in the cover 2l and the inner end of the pivot pin being pointed as shown and journaled in a suitable bearing or socket member 38 in the bottom of the shell 25. The second pivot pin 28 carrying the second rotary member 21, is pointed at both ends, being journaled at its lower end in a socket member 35 in the bottom of the shell 213 and being journaled at its upper end in an adjustable socket member d in the form of a screw mounted in the cover 2 I.

In accord with the underlying concept of the invention, the two rotary members 25 and 21 are interconnected by a flexible conductor 44 in such manner that the flexible conductor lies against the peripheries of both rotary members. In the particular construction shown, the flexible conductor Il is in the form of a loop of extremely flexible wire with one end of the loop engaginga lug l5 on the rotary member 25 and the other end or" the loop engaging a similar lug 46 on the second rotary member 21.

A feature oi this particular embodiment of the invention is the concept of providing suitable yielding means to interconnect the two rotary members 25 and 21 in opposition to the flexible conductor d. Thus, as best shown in Figure l, the two rotary members may be interconnected by a coiled spring 41, one end of which is anchored to a lug 38 on the rotary member 25, the other end of which is anchored to a similar lug 49 on the second rotary member 21. The spring 51 not only co-operates with the flexible conductor It for the purpose of operatively interconnecting the two rotary members 25 and 21, but also serves as means to maintain the flexible conductor constantly under tension thereby eliminating backlash.

It is to be noted that with the parts constructed and arranged as indicated in Figure l, the length of the coiled spring 41 does not vary significantly over the operative range of rotation of the two rotary members 25 and 21, consequently, the coiled spring does not have any troublesome tendency to urge two rotary members to any particular relative positions. Thus, the two rotary members tend to remain in whatever position to which they are moved by the knob 35.

Two suitable resistors 5| and 52, respectively, are mounted on the two rotary segmental members 25 and 21, respectively, each of the resistors comprisingl a suitable coated wire wound on the arcuate portion 32 of the segmental member. Sucient coating is removed to expose the metal of the successive wire turns to the ilexible conductor lili. With this arrangement the ilexible conductor i4 contacts and shorts an end portion of each resistor and the proportion of each resistor shorted in this manner varies with the simultaneous rotation of the two segmental members, one shorted portion increasing and the other one decreasing or vice versa. It is contemplated that the other ends of the two resistors 5l and 52 that are not shorted by the conductor 44 will be adapted for connection to an electric circuit. For this purpose an ample length of wire 57 connects the resistor 5l with a terminal member 58 that extends to the exterior of the casing and a second similar wire 59 connects the second resistor 52 with a similar terminal 85.

The conductor 45 may be directly connected to a third terminal member Bl, or the same purpose may be served by connecting the shorted end of one of the resistors 5l and 52 to the third terminal member. Thus Figure 1 shows a wire 62 extending from the shorted end of the resistor 52 to the third terminal member 6I, the wire being connected at an intermediate point to a metal clip 53 on the lug d6. If desired, the lug 46 may be in the form of a metal pin so that the conductor lill will also be in electrical communication with the wire 62 through the metal of the pin and the metal of the clip 63.

It will be apparent to those skilled in the art that if the two resistors 5l and 52 are matched and if they are so positioned relative to each other that at the position of the parts shown in Figure 1 the shorted portions are equal, the action of the potentiometer will be equivalent tothe action of represented by the wiring diagram in Figure 11. brush or movable contact 66 that traverses the resistor 61 corresponds to the iiexible conductor 44 and the resistor 61 corresponds to the sum of the two portions of the resistors and 52 that are not snorted by the conductor 44.

Figure 3` shows how the device of Figures 1 and 2 may be modied to serve asa simple variable resistance'device. The construction is largely the same as in Figures 1 and 2 as indicated by the use of corresponding: numerals to designate cor responding parts; The resistor 52 is omitted alongv with the corresponding wire 59 and corresponding terminal 60. The wire 62 is connected directly to the flexible conductor 44. Simultaneous rotation of the two segmental members 25 and 2'1 causes the conductor 44 to progressively increase orprogressively decrease the proportion of thel single resistor 5| that it shorts. This arrangement is equivalent to theconventional rheostat circuity shown in Figure 21 in which a movable contact or brush 68 traverses a resistor 69.

Figures 4, 5 and 6- show how a pair of resistorsmay; be wound spirally on a pair of cylindrical rotary members topermit the range of operation of a voltage divider to be extended without limit. A cylindrical rotary member 14 of non-conducting material, having a pair of suitably journaled trunnions 15, is positioned substantially parallel to a second cylindrical rotary member 16, having a pair of trunnions 11. It is contemplated that the two cylindrical members 141 and 16 will be operatively interconnected for rotation in unison and that suitable actuating means will be provided, for example, an operatingknob 18 connected to one of the trunnions 15.

A resistor 8| is wound spil-ally on the cylindrical member 14, a second resistor 82 is wound spirally onY the second cylindrical member 16 and a exible conductorA 83 is spirally wound on the spiral windings of the two resistors in such man-A ner as to unwind from onto the other resistor one resistor and to wind when the two cylindrical members are rotated in unison. One end of the flexible conductor 83 is connected to one end of thef resistor 8| as indicated fat 84 and the other end is connected to the resistor 82 as indicated at 85.

Preferably each of the two resistors 8| and 82 is in the form of a coated wire 88 wound on a core- 89 that is in the form of iiat strip as best shown in Figure 5, the coating being removed from the wire on the periphery of the resistor to permit conducting contact with the iiexible conductor 83. In the construction shown, the portion of each of the cylindrical. members 14 and 16 on which the corresponding resistor is mounted, is cut away to form a helical groove 90 and a narrow helical rib 9|, the groove serving to seat the resistor and the rib serving as means to keep the ilexible conductor 83 from shifting away from a helical turn of the resistor.

Suitable provisions are made toV connect the free ends of the resistors 8| and 82 and the flexible conductor 83 into an electric circuit. For this purpose the free end of the resistor 8|, i. e. the end that is not shorted by the conductorv 83, is. connected by a wire 92 to a slip ring 93 on the cylindrical member 14, and a stationary brush 94'! in contact with the slipring 93 is connected by a wire 95 to a suitable terminal (not shownl ofr the potentiometer. In like manner, the free endis connected by a wire 98 topotentiometer terminali (not shown) by means of a wire |05.

While the two rotary cylindrical members 14 and 16 spense to rotation of the operating knob 18, pref-- erably the operative interconnection is provided by a flexible member |08 in co-operation with the exible conductor |03. The exible member |08 is wound on the two cylindrical members 14 and 16 in a manner opposite to 18 is rotated clockwise as viewed in Figure 4, the iiexible conductor 83 will act in tension to transmit actuating force to the cylindrical member 16v and, on the other hand, when the cylindrical member 14 is rotated counterclockwise, the actu-- to the secondA ating force will be transmittedl cylindrical member 16 through the iiexible member |08. For this purpose the flexible member drical member 14 in a direction to unwind when the flexible conductor 83 winds on the same cylindrical member and issecond cylindrical member 16 to unwind when the flexible conductor winds onto the second cylindrical member.

Preferably each of the two cylindrical members is formed with a helical guide groove |09 to receive the ilexible member |08, the inner diameter of the helical guide groove being substantially the same as the outer diameter of the helically wound resistors 8| and 82. The opposite ends of the exible member |08- may be anchored to the cylindrical members 14 and 15, respectively, as indicated at ||0 and Preierably the member is elastic and is continuously stressed in tension thereby to maintain the ilexible conductor 83 in tension with consequent elimination of backlash. For example, the member |08 may be a multiple strand pre-twisted nylon cord.

It may be readily understood by those skilled' in the art that the described arrangement-shown in Figures 4, 5 and 6 is equivalent to the voltage dividing circuit shown in Figure 11. Figure 7 shows how one or the two resistors in Figure 4k may be omitted to make the arrangement equivaient to the simple rheostat circuit shown in Figure 12.

Figure 7 shows two spaced rotary cylindrical members H5 and SIB with a resistor H1 woundl helically on the cylindrical member [E in the manner heretofore described. A ilexible conductor ||8 is wound onto the resistor ||1 and isconnected to one end of the resistor as indicated The Flexible conductor ||8 is wound' helically on the second cylindrical member ||5 in a helical groove |20 and is anchored to the second cylindrical member as indicated at 2|. One end of the resistor H1, asv well' as the corresponding end of the flexible conductor |18, is connected by a wire |24 to a slip ring |25 and a brush |26-, fio-operating with the slip ring, is corr-` wrapped aroundY the` nected by a wire |21 to a suitable terminal (not shown). In like manner, the other end of the resistor H1 is connected to a slip ring |28 by a wire |29 and a brush |30 adjacent the second slip ring is connected by a wire |31 to a second terminal (not shown).

Any suitable means may be employed to operatively interconnect the two cylinders H5 and ||6 and the two cylinders may be actuated, for example, by an operating knob |35 connected to the cylindrical member ||5. Preferably the required operative interconnection between the two cylindrical members is accomplished by providing a flexible member |08 to cooperate with the flexible conductor as heretofore described, the flexible member being preferably guided by the usual helical grooves |20 in the two cylindrical members.

The purpose of Figures 8, 9 and 10 is to indicate how the principles of the invention may be embodied, with outstanding advantages, in an accelerometer. The general arrangement of the accelerometer is similar to the arrangement shown in Figures l and 2, as indicated by the use of corresponding numerals to indicate corresponding parts. The construction differs only in the omission of the manual actuating means and inthe substitution of a pair of opposed springs Idil for the single spring 41.

The rotary segmental member 25, like the rotary segmental member 21, is mounted on a pin 28 that is pointed at both ends and is journaled in a lower socket member 39 in the shell 2G and an upper socket member 40 in the form of a screw threaded into the cover 2 la. Each of the two springs |40 is iixedly anchored to the shell 2D at one end and at its other end is connected to the corresponding rotary segmental member 25 or 26, the two springs being in opposition to place the flexible conductor lid under tension.

It will be readily apparent that the two springs |40 will cause the two rotary segmental members 25 and 21 to seek a neutral equilibrium position shown in Figure 9 with the two springs in static balance with each other. Since the centers o gravity of the two segmental members are offset from the axes of rotation, being located substantially on the line interconnecting the two pivot pins 28, it is apparent that the two segmental members will respond by rotary displacement to acceleration forces. The maximum response of the two rotary members will be to forces perpendicular to the line interconnecting the two pivot pins. The magnitude of displacement of the two segmental members will be accurately reflected in the change in proportions of the two resistors 5i and 52 that are shorted by the exible conductor 44.

All forms of the invention are characterized by the use of a liexible conductor that makes wiping contact instead of frictional sliding contact with a co-operating resistor. Consequently all forms of the device are advantageous in requiring exceptionally small operating force and in operating with minimum wear. The fact that the ilexible conductor makes contact with each of the two resistors at multiple points closely spaced together insures continuous electrical communication between the flexible conductor and the two resistors.

My description and speciiic detail of selected embodiments of the invention for the purpose ci illustration oi the underlying principles will suggest to those skilled in the art various change substitutions and other departures from my dis- 1 acter described,

d closure that properly lie within the spirit and scope oi the appended claims.

I claim: I

l. In a variable resistance device of the character described, the combination of a first member adapted to rotate about an axis therethrough; a flexible conductor having one end connected to said member for progressive wrapping contact with the periphery thereof when the member rotates in one direction and to peel progressively out of contact with the periphery when the member rotates in the opposite direction; a second member connected to the other end of said conductor and movable to feed the conductor to the first member when the rst member rotates in one direction and to take up the conductor progressively when the first member rotates in the opposite direction; and a resistor on one of said members positioned to be progressively shorted by said conductor when said first member rotates in one direction and vice versa, said ilexible conductor and said resistor being adapted for connection with an electric circuit.

2. A device as set forth in claim l in which said resistor is mounted on the periphery of said rotary member and extends in a generally circumferential direction.

3. A device as set cludes yielding means to maintain said flexible conductor under tension.

fl. A device as set forth in claim 3 in which said yielding means interconnects said two members in opposition to said flexible conductor.

5. in a variable resistance device oi the charthe combination oi: two spaced rotary members adapted to rotate simultaneously, at least one of said two rotary members having a peripheral resistor and a flexible conductor extending from the periphery of one of said rotary members to the periphery of the other in peripheral contact with said resistor for variable shorting thereo'whereby simultaneous rotation of said two members causes said conductor to peel o the periphery or one of the members and to make progressively increasing wrapping contact with the periphery of the other, thereby to progressively vary the proportion of said resistor that is shorted by the conductor, said resistor and conductor being adapted for connection with an electric circuit.

6. A device as set forth in claim 5 which includes yielding means connected to said two r0- tary members to maintain said conductor in tension.

'7. A device as set forth in claim 6 in which said yielding means interconnects said two members in opposition to said iiexible conductor.

8. A device as set forth in claim 7 in which said yielding means is in wrapping contact with said two members in a manner opposite to the wrapping contact or said flexible conductor.

9. A device as set forth in claim 5 which includes two yielding means connected. to said two rotary members respectively, with the two yielding means inopposition to urge said two rotary members to positions oi equilibrium with said yielding means in balance with each other.

l0. A device as set forth in claim 5 in which said two spaced rotary members are of the configuration of a segment of a circle, each being pivotally mounted for rotation about its axis of curvature.

11. A combination as set forth in claim 5 in which at least one of said two rotary members has its center o gravity offset from its axis of forth in claim l which inrotation whereby the member responds to acceleration and which includes yielding means to hold said `acceleration-responsive member in a normal neutral position.

12. In a variable resistance device of the character described, the combination of: two spaced rotary members, at least one of said rotary members having a` peripheral resistor; a flexible conductor extending from the periphery of one of said rotary members to the periphery of the other, in peripheral contact with said resistor whereby simultaneous rotation of the two members causes said conductor to wrap progressively against said resistor and simultaneous rotation in the other direction causes the conductor to Deel 01T said resistor thereby to progressively Vary the proportion of the resistor shorted by the conductor, said resistor and conductor being adapted for connection with an electric circuit; and a exible member interconnecting the peripheries of said two rotary members in wrapping contact therewith opposite with respect to the wrapping contact by said conductor, whereby the conductor and iiexible member co-operate to operatively interconnect the two members so that rotation of one member is transmitted to the other member.

13. A device as set forth in claim 12 in which said flexible member is a longitudinally yieldable member under tensile stress to place said conductor under tension for the elimination of backlash.

14. In a variable resistance device of the character described, the combination of: two spaced rotary members; two corresponding resistors mounted on the peripheries of said two members respectively and extending in generally circumferential directions thereon; and a iiexible conductor having its opposite ends connected to said members respectively in contact with said resistors respectively for progressive wrapping contact from one end of each resistor towards the other end of the resistor and for alternate peeling action in the direction from said other end towards said one end of the resistor whereby simultaneous rotation of the two rotary members progressively varies the proportion of each resistor shorted by the conductor, said conductor and said other ends of said resistors being adapted for connection with an electric circuit.

15. A device as set forth in claim 14 which includes yielding means to maintain said flexible conductor under tension.

16. A device as set forth in claim 15 which includes yielding means connected to both of said rotary members.

17. A device as set forth in claim 16 in which said yielding means interconnects said two rotary members in opposition to said conductor.

18. A combination as set forth in claim 14 which includes a flexible member interconnecting the two rotary members in opposition to said flexible conductor and co-operating with the flexible conductor to operatively interconnect the two rotary members.

19. A device as set forth in claim 18 in which said flexible member is a longitudinally resilient member under tensile stress.

20. A device as set forth in claim, 14 in which said two rotary members have their centers of gravity offset from their axes of rotation for response to acceleration forces applied to the device and which includes means to yieldingly bias said two rotary members to normal neutral positions.

21. In a variable resistance device oi' the character described, the combination of a cylindrical rotary member; a resistor wrapped around the periphery of said rotary member and forming a plurality of spiral turns thereon; a flexible conductor having one end connected to said rotary member in wrapping Contact with said resistor to follow said spiral turns for shorting a variable portion of the resistor; and take up means to feed said conductor to said rotary member when the member rotates on one direction and to peel off the conductor when the rotary member rotates in the opposite direction, said resistor and said conductor being adapted for connection with an electric circuit.

22. A device as set forth in claim 21 which includes yielding means to maintain said iiexible conductor under tension.

23. A device as set forth in claim 22 in which said take-up member is a second rotary cylindrical member with said exible conductor wound thereon.

24. A device as set forth in claim 23 which includes a flexible member wound on said two cylindrical members in an opposite manner from said conductor to co-operate with the conductor for operatively interconnecting the two members for simultaneous rotation.

25. A device as set forth in claim 24 in which said llexible member is longitudinally resilient and is stressed in tension to maintain said conductor under tension thereby to eliminate backlash.

26. In a variable resistance device of the character described, the combination of two rotary cylindrical members; two corresponding resistors, each wound around the periphery of the corresponding cylindrical member to form a plurality of spiral turns thereon; a flexible conductor having its opposite ends connected to said two rotary cylindrical members respectively in wrapping contact with both said resistors to follow the spiral turns thereof for shorting variable portions of the two resistors whereby simultaneous rotation of the two cylindrical members in one respect increases one of said portions and decreases the other portion, and rotation in the opposite respect decreases said one portion and with an electric circuit.

27. A device as set forth in claim 26 which includes yielding means to maintain said conductor in tension.

28. A device as set forth in claim 26 in which at least one of said two cylindrical members has a spiral groove to receive said conductor.

29. A device as set forth in claim 26 which includes means to actuate one of said two cylindrical members and in which the two cylindrical members are operatively interconnected for actuation of the other cylindrical member.

30. A device as set forth in claim 29 which includes a flexible member wound on said two rotary members in opposite respect to said flexible conductor to co-operate with the flexible conductor for operatively connecting the two cylindrical members together.

31. A device as set forth in claim 30 in which said flexible member is a longitudinally resilient member under stress to maintain said flexible conductor in tension. 

